What does the "UR" mean on the cs bday items

[AbyssalRuins]

What does the UR mean for the birthday pancakes and spring cake? Does it mean Ultra rare?

[Waytown]

UR on CS means Unreleased! Meaning they were items from a previous year that had not been released until now, as a special release. Unreleased items are super rare, sometimes rarer than some of the rarest items in-game, so don't trade them away until you know for sure what they're worth!

Edit: the UR Pancakes Cake seems to be based on the UR Pancakes pet from last December, so the name may simply be referring to the UR Pancakes pet.

[Celozon]

They are based on the two UR pets we got last advent, so I believe its just referring to the fact that its based on UR pets, not that the items themselves are UR; archive/2023/Special%20Releases/

We did get UR items last advent that are also cakes based on UR pets so its a bit understandably confusing, those are the only true 'UR' items that exist though. Whether a pet or item counts as UR is really just dependent on how its released. UR pets and items are released on Dec 18th during the annual re-release, and there is only a very small chance to adopt them, so any normal free item release whether everyone gets the same items isn't going to be considered a true UR.